The invention relates generally to a clamping device and, more particularly, to a clamping device that may be specially adapted for use in effecting a seal between components of mass flow controllers used in the manufacture of semiconductor devices.
Semiconductor devices are mass produced by forming many identical circuit patterns on a single silicon wafer which is thereafter cut into many identical dies or xe2x80x9cchips.xe2x80x9d Semiconductor devices, also commonly referred to as integrated circuits, are typically constructed by successively depositing or xe2x80x9cstackingxe2x80x9d layers of various materials on the wafer. Many of these layers are etched according to a predetermined pattern as part of the formation of the desired circuit components. Some of these materials are deposited, patterned and etched using processing techniques that require the introduction of gases into a reaction chamber or vessel. The gases react with one another and with the surface of the semiconductor wafers to deposit or remove the desired materials. For example, chemical vapor deposition (xe2x80x9cCVDxe2x80x9d) and dry or xe2x80x9cplasmaxe2x80x9d etching are two common semiconductor manufacturing processes that use reactant gases to deposit materials on and selectively remove materials from the surface of a semiconductor wafer.
Mass flow controllers are used to monitor and control the flow of the gases into the reaction chamber in CVD, plasma etching and other such semiconductor manufacturing processes. Mass flow controllers are used whenever accurate measurement and control of gas is required. A typical mass flow controller has two primary operational componentsxe2x80x94a mass flow meter and a proportioning controller. The flow meter measures the actual flow. The controller drives a variable displacement valve to the correct position to maintain the desired flow. The gas flows through three primary and discrete physical components in the mass flow controllerxe2x80x94the inlet, the main body and the outlet. In one common configuration, the variable displacement valve is positioned in the inlet and the flow meter is positioned in the main body. Each of the above described components must be sealed one to the other to achieve effective operation of the mass flow controller. Mass flow controllers must be periodically disassembled for cleaning and repairing or replacing worn or malfunctioning parts. Upon re-assembly, care must be taken to ensure that the respective components are properly sealed. The latest generation of mass flow controllers, such as a Unit Instruments, Inc. Model UFC-1600 or Precision Flow Devices Model PFD 501M, utilize metal seals to effect a seal between the component surfaces. Metal seals require that the components be precisely aligned to effect the uniform distribution of tightening forces before the fasteners are tightened to secure and seal the components. In addition, metal seals require the application of much higher torque values to adequately tighten the fasteners.
Experience with the metal seals used in modern mass flow controllers has shown that it is difficult to obtain an effective seal unless the mass flow controller components are clamped together with evenly distributed pressure. The fasteners can then be uniformly tightened to meet the required torque specifications. In the past, the mass flow controller components were clamped together using an ordinary bench mounted vice. Obtaining a satisfactory seal using a vice is difficult and time consuming, particularly because the controller could not be readily and properly positioned for clamping. Unit Instruments, Inc. developed a prototype clamping device for use with its mass flow controllers. Like the bench vise, the Unit prototype did not afford the operator any way to support and accurately position the controller for clamping. The absence of a support/positioning mechanism and its substantial weight made the Unit prototype cumbersome to use and ineffective in consistently obtaining a reliable seal. The Unit prototype also was not adaptable for use with other brands of mass flow controllers.
Accordingly, the present invention is directed to a clamping device that may be specially adapted for use in sealing together the components of mass flow controllers such as those used in the manufacture of semiconductor devices. The invented-clamping device is lightweight, easy to use and it is configurable to use with different brands and models of mass flow controllers. The invention may also be applied to work pieces other than a mass flow controller.
In one embodiment of the invention, the clamping device includes a front member, a back member opposing the front member, a pair of opposing side members, a stop block and a clamping mechanism. The side members extend between and connect the front member and the back member. The work piece is supported by and between the side members. The stop block is interposed between the back member and the work piece. The clamping mechanism, which is operatively coupled between the front member and the work piece, exerts a clamping force against the work piece to press the work piece against the stop block. In this way, the work piece is clamped between the front member and the back member.
In a second embodiment, the clamping device comprises an H shaped front end piece having a cross member extending between two upright members, a back end piece having two upright members, a pair of opposing side plates, a stop block and a clamping mechanism. Each of the side plates extends, respectively, between the upright members of the front end piece and the back end piece. The front end of the side plates is fastened to the upright members of the front end piece, The back end of the side plates is fastened to the upright members of the back end piece. Thus, the front end piece and the back end piece are connected through the side plates. A support rail is formed along the inner surface of each side plate. The support rail is sized and shaped to support the work piece. The stop block is removably interposed between the back end piece and the work piece. The clamping mechanism is operatively coupled between the front end piece and the work piece. The clamping mechanism exerts a clamping force against the work piece to press the work piece against the stop block.
In a third embodiment of the invention, the clamping device is specially adapted for use with a mass flow controller as the work piece. In this embodiment, the stop block consists of two or more interchangeable stop blocks. Each stop block is configured for use in sealing the various components of the controller based on the controller""s orientation in the clamping device. That is, a first stop block is interposed between the back end piece and the controller when the controller is positioned in a first orientation to, for example, seal the inlet to the main body. A second stop block is substituted for the first stop block when the controller is re-oriented to a second orientation to, for example, seal the outlet to the main body.